U.S. patent number 4,499,211 [Application Number 06/402,266] was granted by the patent office on 1985-02-12 for open-cell/microporous molded article.
This patent grant is currently assigned to Hoechst Aktiengesellschaft. Invention is credited to Jurgen Kuhls, Wolfgang Michel, Walter Seifried, Axel Walch, Jurgen Wildhardt.
United States Patent |
4,499,211 |
Walch , et al. |
February 12, 1985 |
Open-cell/microporous molded article
Abstract
The present invention relates to molded articles of an open-cell
structure, containing a copolymer which is comprised of
copolymerized, fluorinated olefin, copolymerized vinyl acetate and
optionally copolymerized olefin, the acetate groups of the
copolymer being optionally saponified into OH groups. The molded
articles possess an inherent latent structural convertibility and
have effective pores of a diameter in the range from 0.002 to 10
.mu.m. The invention further includes processes for the preparation
of the specified molded articles and processes for converting their
structure. The invention also relates to several uses of molded
articles according to the invention.
Inventors: |
Walch; Axel (Frankfurt,
DE), Seifried; Walter (Wiesbaden, DE),
Michel; Wolfgang (Wiesbaden, DE), Kuhls; Jurgen
(Burghausen, DE), Wildhardt; Jurgen (Huenstetten,
DE) |
Assignee: |
Hoechst Aktiengesellschaft
(Frankfurt am Main, DE)
|
Family
ID: |
6137916 |
Appl.
No.: |
06/402,266 |
Filed: |
July 27, 1982 |
Foreign Application Priority Data
|
|
|
|
|
Jul 28, 1981 [DE] |
|
|
3129745 |
|
Current U.S.
Class: |
521/145;
210/500.22; 210/500.42; 264/41; 521/61; 521/62; 521/64 |
Current CPC
Class: |
A61L
15/225 (20130101); A61L 15/425 (20130101); C08J
9/28 (20130101); G03G 7/0073 (20130101); G01N
33/521 (20130101); G01N 33/545 (20130101); G03C
1/795 (20130101); G03G 7/0006 (20130101); G03G
7/004 (20130101); G03G 7/006 (20130101); D01D
5/24 (20130101); C08J 2201/0544 (20130101); C08J
2327/12 (20130101); C08J 2329/04 (20130101) |
Current International
Class: |
A61L
15/42 (20060101); A61L 15/44 (20060101); A61L
15/22 (20060101); A61L 15/16 (20060101); B41M
1/30 (20060101); B41M 5/00 (20060101); B41M
1/26 (20060101); B41M 5/36 (20060101); C08J
9/28 (20060101); C08J 9/00 (20060101); D01D
5/00 (20060101); D01D 5/24 (20060101); G01N
33/545 (20060101); G03C 1/795 (20060101); G01N
33/52 (20060101); G01N 33/544 (20060101); G03G
7/00 (20060101); C08F 009/28 () |
Field of
Search: |
;210/500.2
;521/64,61,62,145 ;264/41 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
12557 |
|
Apr 1979 |
|
EP |
|
1214395 |
|
Apr 1966 |
|
DE |
|
1544928 |
|
Jun 1974 |
|
DE |
|
2364243 |
|
Apr 1978 |
|
FR |
|
1155531 |
|
Jun 1969 |
|
GB |
|
Primary Examiner: Foelak; Morton
Attorney, Agent or Firm: Schwartz, Jeffery, Schwaab, Mack,
Blumenthal & Koch
Claims
What is claimed is:
1. A microporous molded article having an open-cell structure and
comprising a thermoplastic material which possesses an inherent
latent structural convertibility and includes effective pores of a
diameter in the range from about 0.002 to 10 .mu.m, said
thermoplastic material comprising at least about 70 percent by
weight of a terpolymer which is composed of from about 20 to 80
percent by weight, relative to the total weight of the terpolymer,
of copolymerized fluorinated olefin selected from the group
consisting of ethylene and propylene, up to about 40 percent by
weight, relative to the total weight of the terpolymer, of
copolymerized olefin selected from the group consisting of ethylene
and propylene, and from about 80 to 20 percent by weight, relative
to the total weight of the copolymer, of copolymerized vinyl
acetate, with at least 5 percent of the total proportion of acetate
groups contained in the copolymer being converted by saponification
into OH groups after copolymerization of the specified comonomers
to form the terpolymer.
2. A molded article according to claim 1, wherein said terpolymer
comprises about 30 to 70 percent by weight, relative to its total
weight, of copolymerized tetrafluoroethylene, from about up to 20
percent by weight of copolymerized ethylene, and from about 70 to
30 percent by weight, relative to the total weight of the
terpolymer, of copolymerized vinyl acetate, with at least 5 percent
of the acetate groups contained in the terpolymer being converted
by saponification into OH groups after copolymerization of the
specified comonomers to form the terpolymer.
3. A molded article according to claim 1 or 2, wherein more than
about 80 percent of the acetate groups are converted by
saponification into OH groups.
4. A molded article according to claim 1 or 2, which comprises the
form of a film.
5. A molded article having an open-cell structure and comprising a
thermoplastic material which possesses an inherent latent
structural convertibility and includes effective pores of a
diameter in the range from about 0.002 to 10 .mu.m, said
thermoplastic material comprising at least about 70 percent by
weight of a copolymer which is composed of from about 20 to 80
percent by weight, relative to the total weight of the copolymer,
of copolymerized perfluorinated olefin from the group consisting of
ethylene and propylene, from about 0 to 40 percent by weight,
relative to the total weight of the copolymer, of copolymerized
olefin from the group consisting of ethylene and propylene and from
about 80 and 20 percent by weight, relative to the total weight of
the copolymer, of copolymerized vinyl acetate, with at least 5
percent of the total proportion of acetate groups contained in the
copolymer being converted by saponification into OH groups after
copolymerization of the specified comonomers to form the copolymer.
Description
BACKGROUND OF THE INVENTION
The present invention relates to open-cell/microporous molded
articles with inherent latent structural convertibility, to
processes for the preparation of these articles and to processes
for converting their structure. The invention also relates to
particular uses of the molded articles.
Within the scope of the present specification and claims, the term
"molded article" is intended to include films and tubular bodies,
such as tubings and hollow fibers (capillaries). By definition the
term "molded article" further comprises coatings.
In the present specification and claims, microporous molded
articles are to be understood as including molded articles which
have effective pores of the specified size. The
open-cell/microporous molded articles of this invention are
hereinafter briefly called "open-cell molded articles". Molded
articles according to the present invention are also referred to as
intermediate products.
Open-cell/microporous plastic films are known in the art, for
example, such films comprising polyamide, polysulfone or
polyvinylidene fluoride (U.S. Pat. No. 3,615,024), which are
produced by the so-called "phase inversion process", in which a
polymer solution is cast to give a liquid film and the polymer
dissolved in this liquid film is subsequently coagulated to form a
dimensionally stable microporous plastic film. These prior art
films are capable of absorbing liquid in their pores.
It is possible, however, only to an unsatisfactory degree to
transform the known microporous films by structural conversion into
a physically and/or optically, practically homogeneous and
transparent state, since conversion cannot be brought about
spontaneously, i.e. within a very short period, or the temperature
range in which structural conversion takes place is unfavorably
wide.
A film based on cellulose triacetate, which is capable of absorbing
liquid, is marketed under the registered trademark POROPLASTIC. As
a result of its extremely small pore size, this commercially
available film is transparent. If the liquid-containing film dries
out, its pore structure collapses irreversibly due to shrinkage;
the film cannot be re-hydrated and it also no longer absorbs
liquid.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved
open-cell/microporous molded article.
It is another object of the invention to provide open-cell,
structurally white molded articles, the structure of which remains
intact when their pores are charged with liquid and when they are
subsequently dried.
A further object of the invention resides in providing such molded
articles which can be rendered pervious to light, at the most up to
transparency, by a systematically graduatable conversion of their
structure, wherein the conversion comprises a reduction of the free
porosity in the molded articles, due to the conversion of their
structure, according to a rising perviousness to light.
It is also an object of the invention to provide molded articles of
this type wherein such structural conversion is, at the most,
increasable up to a point at which physical and/or optical
homogeneity of the molded articles is practically reached and which
is achievable by the application of appropriate measures within a
close conversion range and in a short period of time.
Another object of the invention resides in providing a process for
producing the molded articles according to the invention.
It is a further object of the invention to provide a process for
converting the structure of the molded articles of the
invention.
Still another object of the invention is to provide improved
articles of manufacture employing the molded articles of the
invention, for example, envelopes for containing chemical media,
information carriers and devices for use in analytical and/or
diagnostic processes.
In accomplishing the foregoing objects, there has been provided in
accordance with one aspect of the present invention a molded
article, either in the form of a film or a tubular body, having an
opencell structure and comprising a thermoplastic material which
possesses an inherent latent structural convertibility and includes
effective pores of a diameter in the range from about 0.002 to 10
.mu.m. This thermoplastic material comprises at least about 70
percent by weight of a copolymer which is composed of from about 20
to 80 percent by weight, relative to the total weight of the
copolymer, of copolymerized fluorinated olefin, from about 0 to 40
percent by weight, relative to the total weight of the copolymer,
of copolymerized olefin, and from about 80 to 20 percent by weight,
relative to the total weight of the copolymer, of copolymerized
vinyl acetate, with at least 5 percent, and preferably 80 percent,
of the total proportion of acetate groups contained in the
copolymer being converted by saponification into OH groups after
copolymerization of the specified comonomers to form the
copolymer.
In accordance with another aspect of the invention, there has been
provided a process for the preparation of a molded article as
described above, comprising the steps of providing a liquid
solution of 1 to 50 weight percent strength, relative to its total
weight, which contains as the dissolved constituent the
above-described copolymer; forming a shaped article from the liquid
solution; and coagulating the copolymer by treating the shaped
article with a precipitating liquid to form a porous-structured,
dimensionally stable molded article.
According to yet another aspect of the invention, there has been
provided a process for converting the structure of a molded article
described above, comprising the step of subjecting a molded article
to the action of an agent capable of rendering the structure of the
copolymer forming the molded article physically and/or optically
homogeneous. The agent comprises a chemical medium, heat and/or
pressure.
According to still other aspects of the invention there have been
provided a reservoir containing low or high molecular-weight
substances, comprising a molded article, which may be for instance
in the form of an envelope; an information carrier, comprising such
a molded article structurally converted in at least certain
preselected areas, whereby the preselected areas represent
information transferred by the molded article; and a device for use
in analytical and/or diagnostic processes, comprising a molded
article as above described for the separation of substances in
gaseous and liquid phases and for the qualitative or quantitative
evaluation of the separated substances.
Further objects, features and advantages of the present invention
will become apparent from the detailed description of preferred
embodiments, when considered together with the attached figures of
drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. I is a cross-sectional photograph of a film according to the
invention magnified 3000 times and
FIG. II is a photograph taken in cross section of a film with a
physically practically homogeneous structure, produced by
structural conversion of a film as shown in FIG. I (magnification
3000 times).
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Molded articles according to the present invention are suitable for
use as starting products in the manufacture of molded articles,
particularly films, which are or appear to be physically
practically homogeneous, at least within discrete areas which
optionally contain a fluid. The volatile portion of the fluid can
only issue by permeation from the physically practically
homogeneous areas of the molded articles. The time of permeation
depends on the chemical characteristic of the volatile portion of
the fluid.
The invention further relates to the use of such a film as a
sheet-shaped material which is suitable for writing or printing and
on which the applied writing or information either lasts
permanently or disappears again within a certain period of time
after the application thereof. This depends on the writing liquid
used which, according to its chemical composition, does or does not
permanently change the structure of the film. Writing or
information is generated by a selectively-produced optical
homogeneity of the molded article. The product of the invention can
thus also be used for transmitting indirect information (for
example, in originals for copying or tracing and in effects caused
by light.
The film of the present invention or the wall of the tubular body
according to the invention, in each case, preferably has a
thickness in the range from about 0.5 to 800 .mu.m. The film may be
self-supporting, or it may be present on a sheet-shaped substrate,
for example, a stretch-oriented film of polyester or a film of
plasticizer-free polyvinyl chloride. The film or the wall of the
tubular body possesses an open-cell structure with pores which have
an effective diameter in the range from about 0.002 to 10 .mu.m.
The film or the wall of the tubular body may also have an
anisotropic-porous constitution. Owing to their specified
structure, the molded articles are white in daylight.
In terms of their chemical constitution, the molded articles are
characterized in that they comprise at least 70 percent by weight
of film-forming, synthetic copolymer (1) which is composed of 20 to
80 percent by weight, relative to its total weight, of
copolymerized fluorinated olefin, preferably copolymerized
fluorinated ethylene or copolymerized fluorinated propylene,
particularly, however, of copolymerized perfluorinated ethylene; 0
to 40 percent by weight, relative to the total weight of the
copolymer, of copolymerized olefin, preferably copolymerized
ethylene or copolymerized propylene; and 80 to 20 percent by
weight, relative to the total weight of the copolymer, of
copolymerized vinyl acetate, with at least 5 percent by weight,
preferably more than 80 percent by weight, of the total amount of
acetate groups contained in the copolymer being converted by
saponification into OH groups after copolymerization of the
specified comonomers to give the indicated copolymer. By
definition, the term copolymer also includes block copolymers or
mixtures thereof.
The molded article may contain up to 30 percent by weight, relative
to its total weight, of polymers which have a different qualitative
chemical composition than the copolymers of which it is
substantially composed. Such polymers comprise, for example,
polyvinylidene fluoride, polar polyolefins or silicones or mixtures
of these.
Preferably, the molded articles comprise copolymer (2) which is
composed of 30 to 70 percent by weight, relative to its total
weight, of copolymerized tetrafluoroethylene, 0 to 20 percent by
weight, relative to its total weight, of copolymerized ethylene,
and 70 to 30 percent by weight, relative to its total weight, of
copolymerized vinyl acetate, with more than 5 percent by weight,
preferably more than 80 percent by weight, of the total amount of
acetate groups contained in this copolymer being converted by
saponification into OH groups, after copolymerization of the
indicated comonomers to form the copolymer.
The molded articles advantageously comprise, for example, copolymer
(3) which is composed of 45 percent by weight of copolymerized
tetrafluoroethylene, 7 percent by weight of copolymerized ethylene
and 48 percent by weight of copolymerized vinyl acetate, with more
than 80 percent of the acetate groups contained in this copolymer
being saponified into OH groups, after preparation of the
copolymer.
Other preferred molded articles comprise copolymer (4) which is
composed of 58 percent by weight of copolymerized
tetrafluoroethylene, 7 percent by weight of copolymerized ethylene
and 35 percent by weight of copolymerized vinyl acetate, with more
than 80 percent of the acetate groups of the copolymer being, after
preparation of the copolymer, saponified into OH groups.
Particular molded articles comprise two-component copolymer (5)
which is composed of 62 percent by weight, relative to its total
weight, of copolymerized tetrafluoroethylene and 38 percent by
weight of copolymerized vinyl acetate and in which more than 80
percent of the acetate groups are, after preparation of the
copolymer, converted by saponification into OH groups.
The indicated percentages by weight of the amounts of copolymerized
comonomers contained in the copolymers mentioned by way of example
are based on the understanding that they total in each case
100%.
Copolymers of the specified chemical composition can be prepared
according to processes which are well-known to persons skilled in
the art (see U.S. Pat. Nos. 3,445,434 and 2,468,664). The
aforementioned copolymers are, per se, not a subject matter of the
present invention.
Due to the chemical composition of the molecular chains of the
copolymer forming the molded articles of the invention, the latter
are both oleophobic and oleophilic. As a result, they are (even
after conversion of their structure) compatible with differing
substances or liquids, which come into contact with them and which
can thus be quickly exchanged.
After charging their pores with liquid, molded articles of the
invention can be dried again, and thereafter they can be reused.
Their characteristics are not substantially changed by the drying
procedure. Consequently, the structure of the molded articles
remains stable due to their composition, if their pores are filled
with liquid and this liquid is later expelled or is allowed to
evaporate from the pores.
Molded articles according to the present invention are
characterized by an inherent latent, systematically graduatable
convertibility of their structure. After conversion of their
structure, the molded articles are physically and/or optically
practically homogeneous and are, therefore, transparent.
Molded articles of the invention are suitable for use as
intermediate products in the manufacture of physically and/or
optically practically homogeneous, transparent molded articles.
The statement that structurally converted molded articles are
physically practically homogeneous denotes, by definition, that the
film or the wall of the tubular body practically does not comprise
any refracting, free pores. The statement that structurally
converted molded articles are optically homogeneous also denotes,
by definition, that their pores or cavities are, to a large extent,
filled with fluid so that the film has a transparent and/or
homogeneous appearance.
Structural conversion of the molded articles is systematically
controllable by choosing specific conditions under which the
process is carried out. Structural conversion may be conducted via
intermediate stages, in which the film or the wall of the tubular
body has different porosities or different transparencies until the
molded articles are, finally, physically practically homogeneous
and/or transparent.
With an increasing perviousness to light of the molded articles,
their free porosity decreases, i.e., the number and/or size of the
refracting cavities which are present in the film or in the wall of
the tubular body are reduced.
Because of its convertibility into a transparent state, the molded
article of the present invention is referred to as being "latently
transparent".
Via intermediate stages, the structure of molded articles according
to the invention can be converted, until the articles reach a
transparent and/or practically physically homogeneous state, by
subjecting the molded articles to a suitable physical or chemical
measure or to a combination of the two measures.
For example, the following measures are suitable for the structural
conversion of molded articles according to the invention:
1. Action of heat on molded articles of the invention. Depending on
the chemical composition of the copolymer of which the respective
molded article is comprised, the latter is heated to a temperature
in the range between about 50.degree. and 220.degree. C. In this
temperature range, the structural conversion of the molded article
occurs in each case within a relatively narrow temperature zone of
less than about 10.degree. C. and proceeds spontaneously.
2. Treating molded articles of the invention with a gaseous or
liquid medium which is capable of incipiently dissolving the
copolymer of which the molded article is composed, for example,
acetone in a liquid or vaporous form. The duration of the measure
which causes structural conversion depends on the concentration and
on the temperature of the liquid medium. Structural conversion
occurs practically spontaneously.
By the expression "practically spontaneous occurrence of structural
conversion" is to be understood that conversion takes place within
a period of seconds.
It is also possible to convert the structure of molded articles of
the invention, particularly that of a film, by allowing compressive
force to act on the molded article or film.
Structural conversion of molded articles according to the invention
by the action of heat or chemical media, as indicated above, can be
assisted in such a way that these measures are, in each case,
combined with an application of force.
Suitable gaseous or liquid media which are capable of incipiently
dissolving the copolymer of which the respective molded article is
composed and which are applied to obtain a structural conversion of
the molded article include, for example, tetrahydrofuran and low
-molecular aliphatic alcohols, particularly also acetone. These
chemical media are preferably applied in a vaporous form.
Depending on the intensity and/or time of action of the measure(s)
causing structural conversion of the molded articles, the structure
of the latter is converted more or less extensively, as required,
and may finally reach a physically practically homogeneous
state.
If the converting measure involves an application of heat, the
extent of structural conversion can be systematically adjusted,
according to the temperature level and the time of temperature
application. In the case of a sufficient period of temperature
application, structural conversion is practically complete, whereas
it proceeds only partially, if the period of temperature
application is short.
If gaseous or liquid media are used to obtain structural
conversion, it is possible to control conversion by means of the
concentration and time of action of these media.
Structural conversion of the molded articles according to the
invention by the action of heat can, for example, be achieved in
such a manner that the articles are treated with hot air of a
sufficient temperature or are subjected to the influence of
infrared radiation. In molded articles which contain ethylene as
the copolymerized component, such as a film having, for example, a
thickness of 30 .mu.m, structural conversion is obtained by heating
to a temperature of about 90.degree. C. and occurs, in that case,
within a period of about 5 seconds.
Structural conversion into an optically homogeneous, i.e.
transparent, film can also be attained by embedding chemically
inert, liquid media, such as paraffins or halogenated hydrocarbons
or even water in the pores of molded articles according to the
invention. A suitable paraffin is, for example, dodecane. Examples
of suitable halogenated hydrocarbons are trichloroethane or
methylene chloride. Due to their vapor pressures, these liquid
media evaporate from the pores within certain periods of time,
which depend on their respective vapor pressure. After charging
their pores with the above-mentioned liquid media, the molded
articles are rendered transparent in the areas in which the pores
are filled with these media. According to the time required for the
medium to evaporate from the pores of the molded articles, the
latter turn white again after a more or less extended period, as
systematically determined. This reversible structural conversion
can even be accelerated or controlled (particularly in segmented
zones), depending on the kind of fluid embedded, by the application
of physico-chemical gradients (e.g. temperature, light, electrical
potential).
The aforementioned effect is, for example, utilized in films
according to the invention in such a way that transparent zones are
generated in these films, which differ optically in a perceivable
manner from their white surroundings. For this purpose, specified
inert liquid media are segmentally applied to the films, for
example, using a liquid-moistened brush by means of which, for
example, letters, figures or ornaments are applied to or rendered
visible on the film. If suitable liquid media are chosen, these
media evaporate, according to their vapor pressures, more or less
quickly from the pores of the film, so that the zones which were
previously transparent as a result of liquid filling the pores,
turn white again after a more or less short period of time.
If a writing liquid which is capable of causing a permanent
structural conversion of the film is segmentally applied to the
white film, the liquid-treated zone turns irreversibly transparent,
i.e., information applied to the film in this way will last
permanently.
In the first-mentioned application, the film, for example, in the
form of a writing film or information carrying or transmitting
material, can be used several times. On the other hand, in the
last-mentioned case it can only be used once.
As constituents which are essential according to the invention, the
solutions used for preparing molded articles of the invention
comprise copolymers of the above-specified qualitative and
quantitative chemical composition.
In the text which follows, the preparation of molded articles
according to the invention is described by way of example:
Preparation starts out from a liquid solution which contains as the
dissolved constituent from 1 to 50 percent by weight of polymer,
relative to the total weight of the solution. The dissolved
constituent comprises, relative to the total amount of polymer
dissolved in the liquid, at least 70 percent by weight of copolymer
which is composed of 20 to 80 percent by weight, preferably 30 to
70 percent by weight, of copolymerized fluorinated olefin, 0 to 40
percent by weight of copolymerized olefin and 80 to 20 percent by
weight, preferably 70 to 30 percent by weight, of copolymerized
vinyl acetate. At least 5%, advantageously more than 80% of the
proportion of acetate groups contained in the copolymer are
converted by saponification into OH groups after completion of the
copolymerization of the indicated comonomers to form the
copolymer.
Relative to the total weight of the polymers dissolved in the
solution, the latter may contain up to 30 percent by weight, for
example, of polyvinylidene fluoride, polar polyolefin or silicones
or mixtures of these polymers, which differ in their qualitative
chemical composition from that of the specified copolymers.
Preferably, the solution used for the production of the molded
articles contains from 5 to 25 percent by weight of dissolved
constituents, relative to its total weight.
Solvents which are suitable for preparing the solution include, for
example, dimethyl formamide, N-methyl pyrrolidone, dimethyl
sulfoxide, dimethyl acetamide, aliphatic alcohols, acetone and
tetrahydrofuran.
The specified solution is extruded in the form of a liquid film
from the straight slot of a die body or in the form of a liquid
hollow fiber from the annular orifice of a die body and is
introduced into a precipitating liquid. Entry into the
precipitation bath may, for example, be preceded by a retention
period in the air. The copolymer dissolved in the solution is
insoluble in the precipitating liquid, while the solvent is soluble
therein. The precipitating liquid used is, for example, water.
While acting on the liquid film or on the liquid hollow fiber
(depending, for example, on the temperature of the precipitation
bath), the precipitating liquid coagulates the copolymer contained
in the liquid film or liquid hollow fiber, thus forming a
dimensionally stable film or dimensionally stable hollow fiber
comprising the copolymer and having the indicated structure.
The film or the hollow fiber is then freed from any excess liquid
in a drying process, or the precipitating liquid is replaced by
another liquid (for example glycerol).
A film according to the present invention may also be prepared in
such a way that a liquid layer of the above-mentioned copolymer
solution is applied to the surface of a dimensionally stable
support foil, for example, in the form of a metal web, and the
precipitating liquid is then allowed to act upon the liquid layer
on the support foil. The copolymer film thus obtained is stripped
off from the support foil.
If the support used is, for example, a stretch-oriented polyester
film or a film of rigid polyvinyl chloride, which has, for example,
a thickness in the range from 50 to 100 .mu.m, and the
above-described procedure is followed, the two-layer laminate
obtained after the copolymer film has formed and dried upon the
surface of the support film can be used according to the
invention.
The pores of the molded articles of the invention can be charged
with, i.e., filled with, fluid. Fluids are, by definition, intended
to denote any liquids to which the copolymer forming the film of
the invention is resistant, i.e., by which the copolymer is
practically not incipiently dissolved.
Fluids may comprise chemically uniform liquids or solutions or
mixtures of such liquids or solutions.
Fluids may also be composed of liquids which contain chemical
substances dissolved therein. The solvent then acts as the carrier
for the dissolved active chemical substance which penetrates into
the pores of the film together with and through the carrier, when
the fluid is applied to the film in order to fill its pores.
Fluids may furthermore comprise liquids which contain active
chemical substances in a dispersed or emulsified form. Also in this
case, the continuous phase of the fluid serves as the carrier for
the substances which are emulsified or dispersed therein. The
liquid carrier causes the active substances contained in it to
enter into the pores of the film according to the invention, when
the fluid is applied to the film.
An example of a fluid of the first-mentioned kind is an organic
liquid-crystalline phase of 4-methoxybenzylidene-4'-n-butylaniline
(MP 21.degree. C.). Fluids of the second kind include, for example,
a photosensitive sulfonamide of o-naphthoquinone diazide dissolved
in an organic phase (e.g. dodecane).
An example of a fluid containing a proportion of a dispersed or
emulsified active substance is an aqueous suspension of
L-thyroxine, the hormone of the thyroid gland.
Fluids may also contain two or more chemically differing substances
as the active substances which are dissolved, dispersed or
emulsified therein.
By definition, the term "fluids", in a broader sense, is intended
to include also pastes and gels, with the liquid portion of such
pastes and gels constituting the fluid in a narrower sense, since
it is only the liquid portion which penetrates into the pores of
the film according to the invention, when the film is treated with
the paste or gel or is brought into contact therewith.
Suitable gels are, for example, those based on agarose. Such gels
may contain a proportion of water which amounts to about 300% or
more, relative to the weight of the gel-forming polymer. The
aqueous proportion of the gel contains a dissolved active chemical
substance, for example, scopolamine or a nitroglycerol
derivative.
In order to charge the pores with fluid, the film may, for example,
be immersed in a tub filled with the fluid. After removing the film
from the tub, any excess fluid present on its surface may be
brushed, squeezed or wiped off.
It is also possible to charge only the pores of segmental areas of
the molded articles with fluid. The procedure employed for this
purpose is explained with reference to an example of a film
according to the invention:
To start with, all pores of the film are filled with fluid in the
above-described manner. Then the structure of the film is converted
in a segmental area, for example, by allowing acetone vapor to act
on this area. Within the structurally converted segmental area of
the film, fluid is contained immobilized in the pores.
In the process, the film which is, as a whole, charged with fluid
is appropriately covered with a mask prior to converting its
structure. This mask corresponds in shape and dimensions to the
film and has differently shaped openings which, for example, form a
sreeen of rectangular apertures. Acetone vapor is then allowed to
act on the mask in such a way that the areas of the film which are
not covered by the mask are contacted by vapor.
If saturated acetone vapor is used, structural conversion of the
treated segmental area of the film occurs within a period of 30 to
60 seconds.
The mask is then removed and the fluid is extracted from the open
pores of the film by means of a suitable liquid eluant. The fluid
enclosed in the structurally converted segmental areas of the film
is not extracted in the process.
To refill the remaining pores with liquid, the film is treated as
described above. However, the fluid used in the second process step
has a different chemical composition than the fluid used in the
first process step. The structure of the film is then converted as
indicated before.
The product resulting from this process contains two fluids which
have different chemical compositions and are present in defined
areas of the film so that, for example, two substances which are
incompatible as such are incorporated in one film.
It is also possible to conduct the process in such a way that,
after the first charging of the film with fluid in segmental areas
thereof, the entire film is structurally converted. The product of
the process is then a transparent film containing fluid immobilized
in a discrete area.
If, for example, liquid volatile aromatic substances or solutions
containing dissolved aromatic substances or liquid volatile
insecticides or solutions containing such insecticides are used as
the fluids and are enclosed in the film, the indicated active
chemical substances diffuse slowly from the physically practically
homogeneous film or the segmental areas thereof and develop their
desired effect outside of the film. Depending upon the rate of
diffusion of the substances, this effect may be long-lasting. If
the fluid used contains light or heat-sensitivie chemical compounds
or reactive compounds which change their structure or color under
the influence of an electrical potential, a film according to the
invention which contains such fluids immobilized therein can be
used in the field of reproduction technique or for phototechnical
processes.
The color or color intensity of film areas which appear physically
practically homogeneous and transparent as a result of a structural
conversion obtained in the above-described manner and which
optionally contain fluid immobilized therein, corresponds to the
color or color intensity of the enclosed fluids or of the coloring
chemical substances in these fluids.
Below, special uses of films according to the present invention are
described by way of example.
1. Use of the film according to the invention as a temporary
deposit and envelope for drugs, catalysts, enzymes, insecticides,
dyestuffs, liquid crystals, corrosion inhibitors or as a covering
for sterilized goods.
EXAMPLE
An aqueous buffered suspension comprising 50 mg of pilocarpine is
filled into a bag made of 5 cm.sup.2 of film according to the
invention, which is comprised of copolymer (3). The bag is then
tightly sealed and exposed for 30 seconds to a saturated atmosphere
of acetone vapor. In the procedure, the originally white film is
rendered opaque-translucent; at the same time, the pores of the
film undergo a defined restriction so that a desired adjustment of
permeability results. The bag is then suspended in 100 ml of
agitated buffer solution. The kinetics of drug release from the bag
into the surrounding liquid is measured. After a starting-up phase,
the required constant kinetic of zero order is reached at a release
rate of 16 mg of active substance per week.
2. Use of the film for analytical and diagnostic processes, such as
immunodiffusion, immunoelectrophoresis, radioimmunoassay,
agglutination tests and diagnostic test sticks.
EXAMPLE
5 ml of an antigen solution of aqueous buffered human albumin (8
.mu.g) are introduced into a hole for sample application in a
copolymer film according to (5). The film is applied in a layer
thickness of 400 .mu.m to a polyester film (.RTM.Hostaphan 100
.mu.m). It has previously been soaked with a serum containing 14%
of antihuman albumin (rabbit). After a diffusion time of 24 hours
in a moist chamber, the layer is extracted in a physiological NaCl
solution for 48 hours and is immediately afterwards dyed with a
protein dyestuff (0.1% Coomassie Blue) and fixed in acetone vapor
for 60 seconds.
A transparent film is obtained which shows a distinct radial zone
of precipitate and can be quantitatively evaluated in
transmission.
3. Use as a support for reprographic and optical information, e.g.,
for photocopies produced with liquid or dry toners (especially for
overhead projection), as a drafting film, as a substrate for
reprographic films (especially as a support for photoactive
substances), as a thermal "paper" (for example, for thermal
copiers), as an "aperture" for recalling texts and optical
information, for the temporary shielding of light-sensitive layers
(for example, of films and photographic materials) or, in the
reverse case, for the temporary exposure of electro-optical or
reactive systems, for rendering visible information, objects or
spaces for a defined period of time, or as an indicator of vapors,
fluids or specific temperatures.
EXAMPLE A
A white, 50 .mu.m thick layer of a terpolymer film according to (4)
or (3) applied to a polyester film (.RTM.Hostaphan 100 .mu.m) is
placed on an overhead projector and is covered with writing using a
felt-tip pencil soaked with dodecane. A clearly defined lettering
which is transparent or reproduces the color of the background is
obtained in a white surrounding and disappears in a few minutes,
after transmitting the desired information. The film can then be
used again.
EXAMPLE B
A white, 30 .mu.m thick layer of a terpolymer film according to (5)
is exposed under a technical test original on a photocopying
machine (Infotec 1801). It is developed with a liquid toner and is
then thermally fixed at a temperature of about 90.degree. C. A
scratch-resistant transparent film results, which exhibits a very
high resolution of the test lines and is suitable for use as an
original on an overhead projector.
As the films or tubular bodies according to the invention are
weldable, they can be used in a simple manner for the manufacture
of bags. In the procedure, two film pieces of identical shape and
dimensions are, for example, placed one upon the other so that
their edges are in alignment. The film pieces are then welded
together in the area of their edges, leaving one side open so that
the bag can be filled with the product to be packaged. After
filling, the bag is closed as indicated. If a tube section is used,
one of its ends is first closed by welding, and after filling with
the product to be packaged, the opposite end of the tube section is
also sealed by welding.
The product according to the invention is shown by way of example
in the accompanying FIGS. I and II.
In FIG. I, a support film is shown as the bottom layer of a
multiple layer product which includes a porous film having a free
surface 3. Reference numeral 4 designates the interface between the
porous film 2 and the support film 1.
In FIG. II, there is illustrated a film 5 having a physically
practically homogeneous structure. Reference numeral 6 denotes the
surface of this film. The film 5 is shown in a state in which it is
practically detached from the plastic support film 7.
The terms "liquid film" or "liquid tubular body" as used in the
specification and claims is meant to denote "a film consisting of
liquid" or "a tubular body consisting of liquid".
* * * * *